Polymerization initiator paste composition, dental or surgical adhesive and adhesive kit

ABSTRACT

The present invention is a polymerization initiator paste composition which comprises (A) an organoboron compound which is liquid at 25° C. and (B) particles having an average particle diameter of 0.001 to 50 μm and inert to the organoboron compound (A), in an amount of 4 to 400 parts by weight based on 100 parts by weight of the organoboron compound (A), and has a consistency, as measured at 25° C. under a load of 300 g in accordance with a method defined in ISO4823, of 15 to 100 mm. This composition constitutes a dental kit or the like together with a polymerizable monomer separately packaged. According to the present invention, an organoboron compound can be used safely, and because the composition is a paste, it is very easily utilized.

TECHNICAL FIELD

The present invention relates to a polymerization initiator pastecomposition that is favorably used as a polymerization initiator of adental or surgical adhesive, a dental or surgical adhesive using thepaste composition, and a kit of the adhesive. More particularly, theinvention relates to a polymerization initiator paste composition thatis excellent in storage stability, handling properties and economicalefficiency, a dental or surgical adhesive showing excellent adhesion todentin and hard tissue, and a dental or surgical adhesive kit.

BACKGROUND ART

Organoboron compounds, particularly tributylboron (TBB) or TBB partialoxide, have been used for years as polymerization initiators of dentaladhesives because of their excellent adhesion properties to dentin.

TBB, however, is a low-viscosity liquid at a working temperature (roomtemperature) and reacts with oxygen in air at room temperature. Thisreaction is an exothermic reaction, and if TBB that is in contact with acombustible substance such as paper reacts with oxygen, ignition(firing) of the substance sometimes takes place.

On this account, in order to slightly decrease reactivity of TBB tofacilitate handling of TBB, a part of TBB is allowed to react withoxygen previously to form a partial oxide of TBB, and the partial oxideis often employed.

However, even if the partial oxide of TBB comes into contact withoxygen, the reaction proceeds. Therefore, TBB or its partial oxide isfilled in a special syringe container having airtight properties, sothat improvement of handling properties of TBB and simplification of thecontainer have been desired.

Some attempts to inhibit fuming- or firing-causing properties oforganoboron compounds have been heretofore made.

In Japanese Patent Publication No. 37092/1976, there is disclosed adental or surgical adhesive using a product (partially oxidizedtrialkylboron), as a polymerization initiator, obtained by the reactionof trialkylboron, with 0.3 to 0.9 mol of oxygen and decreased in theactivity.

In Japanese Patent Laid-Open Publication No. 11892/1973, there isdisclosed a method to improve safety against fuming by the use of apaste obtained by adding a substance having hydrophobicity andviscosity, such as vaseline, paraffin or silicone (silicone oil), and ifnecessary, an adsorbing agent, such as silicic acid or alumina, totrialkylboron or its derivative.

In Japanese Patent Publication No. 54683/1991 (U.S. Pat. No. 4,676,858,European Patent No. 78994), there is proposed a polymerization initiatorthat is a homogeneous mixture obtained by adding an organic oligomer oran organic polymer, such as silicone oil, wax, oligoester or oligoamide,to an organoboron compound.

In Japanese Patent Laid-Open Publication No. 264509/1991, there isproposed a method to improve safety by the use of a paste obtained byadding a polymerization product of a (meth)acrylic acid alkyl esterhaving a particle diameter of 1 to 100 μm to tributylboron or partiallyoxidized tributylboron.

In Japanese Patent Laid-Open Publication No. 110913/1997, there isdescribed a composition obtained by mixing an organoboron compound withan inert low-boiling solvent and a polymer or an oligomer.

In Japanese Patent Laid-Open Publication No. 95806/2000, it is describedthat a specific oligoester is added as a stabilizer to an organoboroncompound and an organic peroxide is added to a polymerizable reactivecomponent to optimize the time to reach the final strength and theadhesion strength and that an initiator component is enclosed in aplastic ampule made of a laminate of a metal foil and a syntheticmaterial of low oxygen diffusion properties to form a kit.

With regard to TBB, various improvements have been proposed as disclosedin the above publications, but in any of those proposals, there is yetroom for further improvement in the enhancement of handling propertiesof TBB and the simplification of containers.

DISCLOSURE OF THE INVENTION

It is an object of the present invention to provide a polymerizationinitiator paste composition which is a paste or a cream containing aliquid organoboron compound and causing no burning or firing of papereven if it is brought into contact with paper in air, hardly showsstringiness and is activated by oxygen in air to impart highpolymerizability to a polymerizable composition and thereby cure it fora short period of time.

It is another object of the present invention to provide apolymerization initiator composition which hardly shows stringiness, hasbeen improved in the handling properties and the container cost by beingcontained in a general purpose container such as an aluminum tubecapable of accurately measuring out the composition even if the amountused one time is small, e.g., several mg to several ten mg, and isparticularly favorable for a dental or surgical adhesive.

It is a further object of the present invention to provide a dental orsurgical adhesive and an adhesive kit each of which uses theabove-mentioned polymerization initiator composition of the inventionand exhibits high adhesion properties.

The polymerization initiator paste composition of the present inventioncomprises:

(A) an organoboron compound which is liquid at 25° C., and

(B) particles having an average particle diameter of 0.001 to 50 μm andinert to the organoboron compound (A), in an amount of 4 to 400 parts byweight based on 100 parts by weight of the organoboron compound (A), and

-   -   has a consistency, as measured at 25° C. under a load of 300 g        in accordance with a method defined in ISO4823, of 15 to 100 mm.

The dental or surgical adhesive of the present invention comprises:

a polymerization initiator paste composition comprising:

-   -   (A) an organoboron compound which is liquid at 25° C., and    -   (B) particles having an average particle diameter of 0.001 to 50        μm and inert to the organoboron compound (A), in an amount of 4        to 400 parts by weight based on 100 parts by weight of the        organoboron compound (A), and    -   having a consistency, as measured at 25° C. under a load of 300        g in accordance with a method defined in ISO4823, of 15 to 100        mm,

and

-   -   (C) a polymerizable monomer which is packaged separately from        the polymerization initiator paste composition.

The dental or surgical adhesive kit of the present invention comprises:

a first container filled with a polymerization initiator pastecomposition comprising:

-   -   (A) an organoboron compound which is liquid at 25° C., and    -   (B) particles having an average particle diameter of 0.001 to 50        μm and inert to the organoboron compound (A), in an amount of 4        to 400 parts by weight based on 100 parts by weight of the        organoboron compound (A),

having a consistency, as measured at 25° C. under a load of 300 g inaccordance with a method defined in ISO4823, of 15 to 100 mm, and

being extrudable from the container,

and

a second container filled with a polymerizable monomer (C) which iscontained separately from the polymerization initiator pastecomposition.

According to the present invention, by adding a specific powder (B) toan organoboron compound (A), the organoboron compound (A) that is liquidat room temperature is changed to a semisolid having a specificconsistency. The organoboron compound (A) in a semisolid state having aspecific consistency is filled in a tube or a syringe, and the semisolidis extruded in a necessary amount (necessary length) every time it isused, whereby the organoboron compound can be quantitatively determinedand used. Further, because of the given consistency, the pasteorganoboron compound (polymerization initiator paste composition)squeezed (or extruded) retains its extruded shape and dose not run out.The thus extruded paste can be easily mixed with a polymerizablepolymer.

Moreover, the amount of the organoboron compound can be converted into alength of the extruded paste, and therefore, the organoboron compoundcan be quantitatively determined and used without performing acomplicated operation such as metering.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of an example of a container filled with apolymerization initiator paste composition of the present invention.

FIG. 2 is a sectional view of another-example of a container filled witha polymerization initiator paste composition of the present invention.

FIG. 3 is a sectional view of a further example of a container filledwith a polymerization initiator paste composition of the presentinvention.

BEST MODE FOR CARRYING OUT THE INVENTION

The polymerization initiator paste composition, the dental or surgicaladhesive and the adhesive kit according to the present invention aredescribed in detail hereinafter.

The polymerization initiator paste composition of the inventioncomprises (A) an organoboron compound and (B) particles.

The organoboron compound (A) for use in the invention is preferablyliquid at room temperature (25° C.), and is a polymerization initiatorcapable of initiating polymerization of a compound having unsaturatedgroup such as a (meth)acrylic acid ester. Preferred examples of theorganoboron compounds include trialkylboron, alkoxyalkylboron,dialkylborane and partially oxidized trialkylboron. These compounds canbe used singly or in combination.

The trialkylboron is, for example, triethylboron, tripropylboron,triisopropylboron, tributylboron, tri-sec-butylboron, triisobutylboron,tripentylboron, trihexylboron, trioctylboron, tridecylboron,tridodecylboron, tricyclopentylboron or tricyclohexylboron.

The alkoxyalkylboron is, for example, butoxydibutylboron.

The dialkylborane is, for example, 9-borabicyclo[3.3.1]nonane.

The partially oxidized trialkylboron is, for example, partially oxidizedtributylboron. As the partially oxidized trialkylboron, a trialkylboronpartial oxide obtained by the addition of preferably 0.3 to 0.9 mol,more preferably 0.4 to 0.6 mol, of oxygen to 1 mol of trialkylboron isavailable.

Of the above liquid organoboron compounds, trialkylboron or partiallyoxidized trialkylboron is particularly preferably employed. Mostpreferable as the liquid organoboron compound is tributylboron (TBB) orpartially oxidized tributylboron.

As the organoboron compound (A) employable in the invention, a compoundwhich is not liquid at room temperature (25° C.) but can be dissolved ordispersed in a solvent to form a solution or a dispersion is alsoavailable. An example of such an organoboron compound is a phenyl boratecompound.

Examples of the phenyl borate compounds include tetraphenylboron alkalimetal salt, tetraphenylboron triethanolamine salt, tetraphenylborondimethyl-p-toluidine salt, tetraphenylboron ethyl dimethylaminobenzoate,sodium tetrakis(p-fluorophenyl)boron, tetraphenylboron triethylaminesalt, tetraphenylboron dimethylaminoethyl methacrylate salt and sodiumbutyltri(p-fluorophenyl)boron.

The particles (B) for use in the invention are particles which are inertto the organoboron compound (A), are solid at 25° C. and have an averageparticle diameter of 0.001 to 50 μm. These particles (B) can bedissolved or homogeneously dispersed in the organoboron compound (A) toadjust a consistency of the organoboron compound to such a degree thatthe organoboron compound can be extruded quantitatively from, forexample, a tubular container. A semisolid of such a consistency isgenerally called a paste, a jelly or a cream, but in the presentinvention, they are sometimes generically referred to as a “paste”.

In the present invention, it is desirable to use, as the particles (B),particles which are solid at room temperature (25° C.), preferably at37° C. When such particles are used for a curing agent of a dental orsurgical adhesive, there is an advantage that retention of adhesionstrength can be enhanced.

In the present invention, particles which are inert to the organoboroncompound (A) and are solid at 25° C. are used as the particles (B). Theparticles are, for example, polymer particles which do not contain agroup having active hydrogen, such as a hydroxyl group or an aminogroup, and/or inorganic particles. As the particles (B), polymerparticles and/or inorganic particles having an average particle diameterof 0.001 to 50 μm are preferably used. More preferably used as theparticles (B) are polymer particles having an average particle diameterof 0.001 to 30 μm and/or inorganic particles having an average particlediameter of 0.001 to 10 μm, and particularly preferably used are polymerparticles and/or inorganic particles having an average particle diameterof not less than 0.005 μm and less than 1 μm.

In the case where the polymer particles are used as the particles (B) inthe invention, preferred examples of polymers to form the polymerparticles include synthetic polymers, such as poly(meth)acrylic acidesters, polystyrene, butadiene polymers (e.g., MBS), polyacrylonitrile,polyamide (Nylon™), silicone resin, polyurethane, melamine resin,phenolic resin and fluororesin; and natural polymers, such as cellulose,cellulose acetate and chitosan. Of these, poly(meth)acrylic acid estersare particularly preferably employed. In the present invention, theparticles (B) have only to be solid at room temperature, and instead ofthe polymer particles, oligomer particles may be employed. The polymeror the oligomer to form the polymer particles has a molecular weight ofusually 1000 to 1000000. Although the polymer particles may be sphericalor in unfixed shapes, they are preferably spherical.

In the case where the poly(meth)acrylic acid ester particles are used asthe particles (B) in the invention, examples of (meth)acrylic acid estermonomers used to form the particles include alkyl acrylates, such asmethyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate,butyl acrylate, sec-butyl acrylate, isobutyl acrylate, t-butyl acrylate,pentyl acrylate and hexyl acrylate; and alkyl methacrylates, such asmethyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropylmethacrylate, butyl methacrylate, sec-butyl methacrylate, isobutylmethacrylate, t-butyl methacrylate, pentyl methacrylate and hexylmethacrylate. These monomers can be used singly or in combination. Asthe polymer particles, particles prepared by usual polymerization can beused as they are, or their pulvarizates can be used.

In the case where the polymer particles insoluble in the organoboroncompound that is liquid at room temperature are used, polymer particleshaving a smaller average particle diameter are advantageous in that theyexert higher thickening effect when they are mixed with the organoboroncompound, the organoboron compound that is liquid at room temperaturecan be easily pasted even if the particles are added in small amounts,and the resulting paste is excellent in properties, storage stabilityand discharge properties from a discharge nozzle of a container.Further, as the size of the particles is decreased, the influence on theprogress of polymerization reaction becomes smaller when the resultingpolymerization reaction initiator paste composition is mixed with amonomer. Moreover, mixing with the monomer or dispersing becomes easier,and therefore, the influence on the adhesion properties of thepolymerizate becomes smaller.

On the other hand, polymer particles having a relatively larger diameterexert lower thickening effect when they are mixed with the organoboroncompound, so that they can be added to the liquid organoboron compoundin larger amounts than the particles of smaller diameters. As a result,the proportion of the boron compound in the polymerization initiatorpaste composition can be decreased. Accordingly, if the variability ofthe discharge amount (that is proportional to the length of the pastedischarged) of the polymerization initiator paste composition isintended to be decreased, or if the amount of the polymerizationinitiator paste composition is intended to be increased, or if theproportion of the organoboron compound in the polymerization initiatorpaste composition is intended to be adjusted, particles having a largeaverage particle diameter are used singly or in combination withparticles having a small average particle diameter, whereby theprescribed intention can be attained.

In the case where the polymer particles are used as the particles (B) inthe invention, particles soluble in the organoboron compound that isliquid at 25° C. and particles insoluble therein can be properlyselected and used in combination with the proviso that those particlesare inert to the organoboron compound.

That is to say, in a preferred embodiment, polymer particles insolublein the organoboron compound that is liquid at 25° C. are added in largeamounts and polymer particles soluble therein and/or inorganic particlesare added in small amounts.

Further, two or more kinds of polymer particles which are insoluble butdispersible in the liquid organoboron compound and/or inorganicparticles may be used in combination.

In this case, it is preferable to use, as the particles (B), mixtures ofparticles (b1) having an average particle diameter of not less than0.001 μm and less than 1 μm and particles (b2) having an averageparticle diameter of 1 μm to 50 μm, because discharge properties of thepaste from a discharge nozzle having a small inner diameter becomebetter than the case of using only the particles (b2) The mixing ratiocan be arbitrarily selected according to the purpose, and for thepurpose of addition of large amounts of the polymer particles, theparticles (b1) are used in amounts of 5 to 200 parts by weight,preferably 5 to 100 parts by weight, based on 100 parts by weight of theparticles (b2).

As the polymer particles, any of crosslinked particles and uncrosslinkedparticles are properly employed.

The polymer particles may be soluble or insoluble in the polymerizablemonomer component of the adhesive unless they have an influence on theadhesion strength of the adhesive, but the polymer particles soluble inthe liquid organoboron compound are preferably soluble also in thepolymerizable monomer.

On the other hand, the polymer particles insoluble in the liquidorganoboron compound may be soluble or insoluble in the polymerizablemonomer unless they have an influence on the adhesion strength.

The inorganic particles having an average particle diameter of 0.001 to50 μm for use in the invention may be spherical or in unfixed shapes,and the shape and the particle diameter of the particles are properlyselected. As the types of the inorganic particles, publicly known onesare available. For example, there can be mentioned Group I elements,Group II elements, Group III elements, Group IV elements and transitionmetals of the periodic table, their oxides, hydroxides, chlorides,sulfates, sulfites, carbonates, phosphates and silicates, mixturesthereof and composite salts thereof. More specifically, inorganicparticles unreactive to the boron compound are properly selected fromglass powders, such as silicon dioxide, strontium glass, lanthanum glassand barium glass, quartz powder, barium sulfate, aluminum oxide,titanium oxide, barium salt, calcium carbonate, glass bead, glass fiber,barium fluoride, lead salt, glass filler containing talc, colloidalsilica, silica gel, zirconium oxide, tin oxide and other ceramicpowders.

These inorganic particles may be used in combination of two or morekinds, and may be used together with the aforesaid polymer particles.

From the viewpoints of adhesion properties and paste properties, theaverage particle diameter of the inorganic particles is more preferably0.001 to 10 μm, most preferably not less than 0.005 μm and less than 1μm.

Similarly to the polymer particles, by the use of mixtures of inorganicfine particles (b3) having an average particle diameter of not less than0.001 μm and less than 1 μm and inorganic particles (b4) having anaverage particle diameter of 1 μm to 50 μm, discharge properties of thepolymerization initiator paste composition from a discharge nozzlehaving a small inner diameter become better than the case of using onlythe inorganic fine particles (b3) having an average particle diameter ofnot less than 0.001 μm and less than 1 μm. When the particles havingdifferent average particle diameters are used in combination as above,the mixing ratio therebetween can be arbitrarily selected according tothe purpose. For the purpose of addition of large amounts of theinorganic particles, the inorganic fine particles (b3) are used inamounts of 5 to 200 parts by weight, preferably 5 to 100 parts byweight, based on 100 parts by weight of the inorganic particles (b4).

In the polymerization initiator paste composition of the invention, theparticles (B) are contained in amounts of 4 to 400 parts by weight,preferably 5 to 300 parts by weight, particularly preferably 5 to 200parts by weight, based on 100 parts by weight of the organoboroncompound (A).

The polymerization initiator paste composition of the inventioncomprising the organoboron compound (A) and the particles (B) has aconsistency, as measured at 25° C. in accordance with a method definedin ISO4823, of 15 to 100 mm. Adjustment of a consistency of thepolymerization initiator paste composition of the invention in the aboverange makes it possible to fill the polymerization initiator pastecomposition of the invention in a container such as a tube or a syringeand to extrude (or squeeze) the paste composition from a nozzle of thecontainer.

The consistency of the composition of the invention is measured by thefollowing method that is defined in ISO4823. On a glass plate, 0.5 ml ofthe composition is placed at 25° C. using a syringe having an openingdiameter of 10 mm, and on the composition, another glass plate wasfurther placed. Then, a weight is gently placed so that the total weightof the glass plate placed on the composition and the weight should be300±3 g, and after 1 minute, the weight is removed. Then, many pairs ofparallel lines in contact with an outer edge of the shape of thecomposition having spread on the glass plate are drawn, and the maximumvalue and the minimum value between the parallel lines are measured. Themeasured values is calculated and expressed in the unit of 1 mm as theconsistency.

Accordingly, a large value of the consistency means that the paste hascharacteristics that it is liable to run out and can be easily mixedwith the polymerizable monomer but the composition extruded from thecontainer cannot retain its shape and is liable to run out. Therefore,the shape of the extruded paste readily changes, and as a result, errorsin the quantitative relation between the length of the paste extrudedand the amount of the organoboron compound are liable to occur. On thecontrary, a small value of the consistency means that the paste has ahigh viscosity and the shape of the composition extruded from thecontainer is retained. In this case, errors in the quantitative relationbetween the length of the paste extruded and the amount of theorganoboron compound hardly occur, but it becomes difficult to extrudethe composition from the container, and blending properties of thecomposition with the polymerizable monomer are lowered.

The balance between them is extremely improved by adjusting theconsistency of the paste of the invention in the range of 20 to 90 mm,particularly preferably 20 to 80 mm.

The polymerization initiator paste composition of the inventioncomprises the specific organoboron compound (A) and the specificparticles (B) and has a consistency in the specific range, as describedabove. To the polymerization initiator paste composition, however, othercomponents can be added within limits not detrimental to the propertiesof the paste composition.

For example, a polymerization initiator of photopolymerization type maybe further added to the polymerization initiator paste composition ofthe invention.

The polymerization initiator of photopolymerization type(photopolymerization initiator) is preferably one capable of undergoingphotopolymerization when irradiated with visible light. Thephotopolymerization initiator is not specifically restricted providedthat it is unreactive to the boron compound, and examples of suchcompounds include α-diketone compounds such as benzil, diacetyl,d,l-camphorquinone, acylphosphine oxide, ketal compounds, andthioxanthone compounds.

The polymerization initiator of photopolymerization type is used in anamount of usually 0.1 to 50 parts by weight, preferably 1 to 30 parts byweight, more preferably 1 to 20 parts by weight, based on 100 parts byweight of the organoboron compound (A).

The polymerization initiator paste composition of the invention can beused in combination with a reducing compound. As the reducing compound,an organic reducing compound is preferably used. Examples of the organicreducing compounds include aromatic amines, such as N,N-dimethylaniline,N,N-dimethyl-p-toluidine (DMPT), N,N-diethyl-p-toluidine,N,N-diethanol-p-toluidine (DEPT), N,N-dimethyl-p-tert-butylaniline,N,N-dimethylanisidine, N,N-dimethyl-p-chloroaniline,N,N-dimethylaminobenzoic acid and its alkyl esters,N,N-diethylaminobenzoic acid (DEABA) and its alkyl esters, andN,N-dimethylaminobenzaldehyde (DMABAd); N,N-dimethylaminoethyl(meth)acrylate, N,N-diethylaminoethyl (meth)acrylate, N-phenylglycine(NPG), N-tolylglycine (NTG), andN,N-(3-methacryloyloxy-2-hydroxypropyl)phenylglycine (NPG-GMA).

Of these, DMPT, DEPT, DEABA, DMABAd, NPG and NTG can be preferably used.

The organic reducing compound is used in an amount of usually 0.1 to 20parts by weight, preferably 0.5 to 10 parts by weight, more preferably 1to 5 parts by weight, based on 100 parts by weight of the organoboroncompound (A).

The photopolymerization initiator and the reducing compound may bedirectly added to the polymerization initiator paste composition, or maybe used by impregnating a sponge or a microbrush with them and mixingthem with the polymerization initiator paste composition immediatelybefore the paste composition is used.

In the polymerization initiator paste composition of the invention, anon-protonic solvent may be further contained. The non-protonic solventhas a function of controlling the consistency of the paste as a solventfor the organoboron compound (A) and the particles (B), particularly thepolymer particles, and has a function of inhibiting fuming and firingwhen the liquid organoboron compound (A) is brought into contact with acombustible substance.

As the non-protonic solvent, a solvent having a boiling point of usually30 to 150° C., preferably 30 to 120° C., particularly preferably 30 to80° C., is employed.

The non-protonic solvent is preferably a solvent which evaporates orscatters for a short period of time after it is used and does not remainin the cured composition so as not to lower the adhesion properties ofthe adhesive.

As such a non-protonic solvent, a solvent having no active hydrogen of ahydroxyl group, a mercapto group or the like that reacts with the liquidorganoboron compound (A) and capable of dissolving or homogeneouslydispersing the liquid organoboron compound (A) to form a homogeneoussolution (or dispersion) is preferably employed.

Examples of the non-protonic solvents employable in the inventioninclude hydrocarbons, such as pentane, hexane, cyclohexane, heptane,benzene and toluene; halogenated hydrocarbons, such as chlorobenzene,fluorobenzene, dichloroethane and so-called Flon™; ethers, such asdiethyl ether, diisopropyl ether, ethylene glycol dimethyl ether andtetrahydrofuran; ketones, such as acetone, methyl ethyl ketone anddiethyl ketone; and esters, such as methyl acetate, ethyl acetate andisopropyl acetate. Of these, ketones, ethers and esters are preferable,and acetone, methyl ethyl ketone and ethyl acetate are particularlypreferable. These non-protonic solvents may be used singly or incombination of two or more kinds.

The non-protonic solvent is used in an amount of usually 10 to 150 partsby weight, preferably 20 to 100 parts by weight, based on 100 parts byweight of the organoboron compound (A).

The organoboron compound (A) which is liquid at 25° C., the particles(B) which are inert to the organoboron compound and are solid at 25° C.,and if necessary, other components can be mixed by a mixing apparatususually used for preparing a paste, such as a stirring mixer, a staticmixer or a rotating or revolving type stirring defoaming machine, in aninert gas atmosphere, preferably in a nitrogen gas atmosphere.

The polymerization initiator paste composition prepared by, for example,the above process is filled in a container made of a materialimpermeable to air and water vapor and inert to the organoboroncompound, such as metal, plastic or glass, for example, a syringe 20 or40 shown in FIG. 1 or FIG. 2 or a tube 50 shown in FIG. 3, or apackaging bag made of a laminated film of an aluminum foil and a plasticfilm. Then, the container or the bag is sealed. When the polymerizationinitiator paste composition contains a photopolymerization catalyst, alight-screening container is employed.

Examples of the metal materials employable for forming the container tobe filled with the polymerization initiator paste composition of theinvention include metals, such as aluminum, tin, lead, brass andstainless steel, and composite metals, such as nickel-plated brass.

Examples of the plastics preferably used for forming the container to befilled with the polymerization initiator paste composition of theinvention include polyolefin resins, such as polyethylene andpolypropylene, and fluororesins, such as polytetrafluoroethylene (PTFE),polyperfluoroalkyl vinyl ether (PFA), atetrafluoroethylene/hexafluoroethylene copolymer (FEP), an ethylenefluoride/propylene fluoride ether copolymer (EPE) and anethylene/tetrafluoroethylene copolymer (ETFE).

As the material of the tube, a metal such as aluminum or tin ispreferably used singly. A laminated tube formed from a laminate of themetal and a plastic is also preferably used.

In FIG. 1, an example of a syringe filled with the polymerizationinitiator paste composition 10 of the invention is shown. The syringe 20has a cylinder 21 in a cylindrical form that is filled with thepolymerization initiator paste composition 10, a nozzle 22 provided atthe tip of the cylinder 21 and a piston 23 to push out thepolymerization initiator paste composition 10 filled in the cylinder.The cylinder 21 is in a cylindrical form so that the piston 23 can beforced thereinto. The cylinder 21 preferably has light-screeningproperties in order to maintain the thus filled polymerization initiatorpaste composition 10 stable. It is preferable that the rear end of thecylinder 21 is sealed with a sealing lid 24 having at the center aninsertion hole for the piston 23. In the syringe 20 shown in FIG. 1, therear end of the cylinder 21 is provided with a finger grip 25 in theform of a ring for laying a finger to push the piston 23. At the tip ofthe cylinder 21, a nozzle 22 is formed, and in the nozzle 22, aback-flow valve 26 to prevent back flow of the polymerization initiatorpaste composition 10 from the tip of the nozzle 22 is preferablyarranged. When the back-flow valve 26 is arranged, the back-flow valve26 is usually powered in the direction of the rear end of the cylinder21 by means of an elastic member 27. The nozzle 22 is fixed to the tipof the cylinder 21 and has an inner diameter D of such a degree that thepolymerization initiator paste composition 10 having the aboveconsistency can be extruded. Further, the nozzle 22 has a given length Lso that the polymerization initiator paste composition 10 filled in thecylinder 21 should not be influenced by air or water vapor entering fromthe tip of the nozzle.

It is preferable to arrange a cap 30 on the nozzle 22 so that air or thelike hardly invades from the tip of the nozzle 22. The cap 30 ispreferably provided with a rubber hold-down member 31 at the positionthat is brought into contact with the tip of the nozzle 22, and when thesyringe is not used, the tip of the nozzle 22 is held down by the rubberhold-down member 31 to prevent contact of the polymerization initiatorpaste composition 10 present at the tip of the nozzle 22 with air or thelike. It is also preferable that the cap 30 is formed so as to be unitedwith the syringe 20 by means of, for example, a circular groove 29 whichcan be fitted to a circular protrusion 28 formed on the outer peripheryof the cylinder 21. The cap 30 may be formed so as to be screwed intothe syringe 20.

The polymerization initiator paste composition 10 of the invention canbe filled in such a simple syringe 40 as shown in FIG. 2 instead of theabove-mentioned syringe.

Similarly to the syringe 20 shown in FIG. 1, the syringe 40 containingthe polymerization initiator paste composition 10, which is shown inFIG. 2, has a cylinder 41 in a cylindrical form that is filled with thepolymerization initiator paste composition 10, a nozzle 42 provided atthe tip of the cylinder 41 and a piston 43 to push out thepolymerization initiator paste composition 10 filled in the cylinder.

The cylinder 41 and the piston 43 of the syringe 40 have the sameconstitutions as those of the syringe 20 shown in FIG. 1. Also thesyringe 40 is provided with a finger grip 45, but the finger grip 45 isnot in the form of a ring.

The nozzle 42 to constitute the syringe 40 is shorter than the nozzle toconstitute the syringe shown in FIG. 1, and in the nozzle 42, aback-flow valve is not provided. The nozzle 42, however, has a givenlength L and has an inner diameter D of a given value so that thepolymerization initiator paste composition 10 can be discharged in agiven length and in a necessary amount.

It is preferable to arrange a cap 30 on the nozzle 42 so that air or thelike hardly invades from the tip of the nozzle 42. The cap 30 ispreferably provided with a rubber hold-down member 31 at the positionthat is brought into contact with the tip of the nozzle 42, and when thesyringe is not used, the tip of the nozzle 42 is held down by the rubberhold-down member 31 to prevent contact of the polymerization initiatorpaste composition 10 present at the tip of the nozzle 42 with air or thelike. It is also preferable that the cap 30 is formed so as to be unitedwith the syringe 40 by means of, for example, a circular groove 49 whichcan be fitted to a circular protrusion 48 formed on the outer peripheryof the cylinder 41. The cap 30 may be formed so as to be screwed intothe syringe 40.

The polymerization initiator paste composition 10 of the invention maybe filled in such a tube 50 as shown in FIG. 3.

The tube 50 has a tube body 51 and a nozzle 52, and the nozzle 52 isformed so as to be screwed into the top of the tube body 51. Into thenozzle 52, a cap 30 is screwed, whereby the polymerization initiatorpaste composition 10 present at the tip of the nozzle 52 can beprevented from contact with air or water vapor.

The tube body 51 of the tube 50 is usually formed from a light-screeningmaterial, and is formed from a material impermeable to air, moisture andthe like.

The nozzle 52 connected to the tube 51 has an inner diameter D of such adegree that the polymerization initiator paste composition 10 having theaforesaid consistency can be extruded in a given length and in anecessary amount, and has a given length L so that the polymerizationinitiator paste composition 10 filled in the tube body 51 should not beinfluenced by air, water vapor or the like entering from the tip of thenozzle 52 and that the discharge operation can be carried out easily.

In FIG. 3, an embodiment wherein a back-flow valve is not arranged inthe nozzle 52 is shown, but such a back-flow valve and such an elasticmember as shown in FIG. 1 may be arranged.

It is preferable to arrange a cap 30 on the nozzle 52 so that air or thelike hardly invades from the tip of the nozzle 52. The cap 30 ispreferably provided with a rubber hold-down member 31 at the positionthat is brought into contact with the tip of the nozzle 52, and when thetube is not used, the tip of the nozzle 52 is held down by the rubberhold-down member 31 to prevent contact of the polymerization initiatorpaste composition 10 present at the tip of the nozzle 52 with air or thelike. The cap 30 is screwed onto the outer periphery of the nozzle 52 toensure the contact of the tip of the nozzle 52 with the rubber hold-downmember 31 of the cap 30.

In case of dental use, the amount of the polymerization initiator pastecomposition of the invention used one time is usually in the range of 10to 20 mg.

In the container such as a syringe or a tube, the polymerizationinitiator paste composition of the invention is introduced in an amountof usually 0.5 to 5 g as the amount corresponding to several tens times.The structure or the material of the container needs to be impermeableto oxygen, water vapor, and if necessary, light. When the polymerizationinitiator paste composition is used as a curing material of a dentaladhesive, the amount of the curing material has an influence on the potlife, curing time and adhesion properties, so that it is necessary tomeasure a prescribed amount accurately to a certain extent. For example,by allowing the amount of the polymerization initiator extruded and thelength of the polymerization initiator extruded to have a correlationwith each other, a metering method of extremely good operatingproperties can be obtained.

The amount of a partial oxide of the organoboron compound such as apartial oxide of TBB used one time for dental purpose is usually about0.01 g. Therefore, in order to obtain a discharge length of about 0.5 to2 cm of the polymerization initiator paste corresponding to this weight,the inner diameter D of the tip of the nozzle of the syringe 20 or 40 orthe tube 50 is in the range of preferably 0.4 to 4 mm, more preferably0.8 to 3 mm, for the accurate metering.

In case of usual handling or storage, the length L of the dischargenozzle of the container has only to be such a length that thepolymerization initiator composition filled in the tube or the syringeis not influenced by oxygen or water vapor. If the discharge nozzle istoo long, it becomes difficult to extrude the polymerization initiatorcomposition of high viscosity. The length L of the nozzle is in therange of usually 2 to 50 mm, preferably 5 to 20 mm, more preferably 5 to15 mm.

In order that the polymerization initiator composition can be easilyextruded from such a fine nozzle and that the extruded composition has afixed size or weight irrespective of the extrusion method, it is veryimportant to control the consistency of the polymerization initiatorcomposition.

It is preferable to provide a cap 30 on the tip of the nozzle of thesyringe 20 shown in FIG. 1 or the syringe 40 shown in FIG. 2 or the tube50 shown in FIG. 3 in order to seal the nozzle when the pastecomposition is not used or is stored. By virtue of the cap 30, contactof the polymerization initiator paste composition of the invention withair or water vapor can be minimized. The cap 30 can be formed from aresin, a metal or the like which is inert to the organoboron compoundsimilarly to the container. At the nozzle contact portion of the cap 30,a rubber hold-down member 31 made of an elastic material such as afluororubber or a silicone rubber is provided to prevent contact of thepolymerization initiator paste composition of the invention with air orwater vapor.

The polymerization initiator paste composition of the inventioncontaining the organoboron compound (A), the particles (B), andoptionally, other components has the following properties: (1) In usualhandling of the paste composition, the composition does not causeburning or firing of paper even if it is in contact with paper; (2) thecomposition is pasty; and (3) the composition is activated by oxygen inair to exhibit high polymerization activity.

The polymerization initiator paste composition can be used for a dentalor surgical adhesive kit.

That is to say, there is provided by the present invention a dental orsurgical adhesive comprising (a) a polymerizable monomer in an amount of20 to 90 parts by weight, (b) a filler in an amount of 0 to 70 parts byweight and (c) the polymerization initiator paste composition of theinvention in an amount of 1 to 30 parts by weight, with the proviso thatthe total amount of the components (a), (b) and (c) is 100 parts byweight.

Further, there is also provided by the present invention a dental orsurgical paste adhesive of two-agent type comprising at least a pastemonomer composition, which comprises (a) a polymerizable monomer in anamount of 30 to 95 parts by weight and (b) a filler in an amount of 5 to70 parts by weight, with the proviso that the total amount of thecomponents (a) and (b) is 100 parts by weight, and (c) thepolymerization initiator paste composition of the invention.

Furthermore, there is also provided by the present invention a dental orsurgical adhesive kit comprising at least a container containing (a) apolymerizable monomer in an amount of 20 to 90 parts by weight, acontainer containing (c) the polymerization initiator paste compositionof the invention in an amount of 1 to 30 parts by weight, andoptionally, a container containing (b) a filler in an amount of 0 to 70parts by weight, with the proviso that the total amount of thecomponents (a), (b) and (c) is 100 parts by weight.

Moreover, there is also provided by the present invention a dental orsurgical paste adhesive kit of two-agent type comprising at least acontainer containing a paste monomer composition comprising (a) apolymerizable monomer in an amount of 30 to 95 parts by weight and (b) afiller in an amount of 5 to 70 parts by weight, with the proviso thatthe total amount of the components (a) and (b) is 100 parts by weight,and a container containing (c) the polymerization initiator pastecomposition of the invention.

To the dental or surgical paste adhesive kit of two-agent type, acontainer containing a filler, e.g., polymer particles such as PMMA, maybe further attached. The filler has functions of improvement andadjustment of curing properties, adhesion properties and color tone ofthe adhesive.

Although the paste monomer and the polymerization initiator pastecomposition may be mixed in an arbitrary ratio, it is preferable fromthe viewpoint of metering operation that the lengths of those pastesextruded are made the same as each other.

That is to say, by making both of the monomer and the polymerizationinitiator composition pasty, their quantities for use can be measured,not in weight, but in length of the pastes extruded.

As the container, the syringe 20 or 40 shown in FIG. 1 or FIG. 2 or thetube 50 shown in FIG. 3 is employable.

The filler (b) for use in the dental or surgical adhesive of theinvention is properly selected from an organic filler (b-1), aninorganic filler (b-2) and an inorganic-organic composite filler (b-3).

The organic filler (b-1) is, for example, a filler of a powder polymerobtained by pulverization of a polymer or polymerization. As the polymerfor forming the organic filler, a homopolymer of the aforesaidpolymerizable monomer or a copolymer thereof is preferably employed.Examples of such polymers include alkyl (meth)acrylate polymers, such aspolymethyl methacrylate (PMMA), polypropyl methacrylate, polybutylmethacrylate (PBMA), poly(ethylene glycol dimethacrylate) andpoly(trimethylolpropane trimethacrylate). As other polymers, there canbe mentioned polyvinyl acetate, polystyrene, their copolymers, andbutadiene copolymers such as MBS.

In the present invention, an organic filler having an average particlediameter of usually 0.005 mμ to 50 μm, preferably 0.01 mμ to 35 μm, isemployed.

Examples of the inorganic fillers (b-2) include silica, silica alumina,alumina, alumina quartz, glass (including barium glass), titania(titanium oxide), zirconia (zirconium oxide), silica zirconia, calciumcarbonate, kaolin, clay, mica, aluminum sulfate, barium sulfate, calciumcarbonate, calcium sulfate and calcium phosphate. Such inorganic fillersmay be those having been surface treated with coupling agents such assilane coupling agents.

In the present invention, an inorganic filler having an average particlediameter of usually 0.005 μm to 50 μm, preferably 0.01 μm to 20 μm, isemployed.

Examples of the organic-inorganic composite fillers (b-3) includefillers obtained by mixing inorganic fillers with polymerizable monomersto perform polymerization and then pulverizing the resulting polymers.Specifically, there can be mentioned, for example, a filler obtained bypolymerization coating of a silica fine powder or zirconium oxide as theinorganic filler with a polymerizable monomer mainly containingtrimethylolpropane trimethacrylate and pulverizing the resultingpolymer.

In the present invention, an organic-inorganic composite filler havingan average particle diameter of usually 0.01 μm to 50 μm, preferably 0.5μm to 25 μm, is employed.

As the polymerizable monomer (a) for the dental or surgical adhesive ofthe invention, publicly known monofunctional monomers or polyfunctionalmonomers can be employed without any restriction. Of such monomers,(meth)acrylate monomers are preferably employed because they arerelatively lowly irritant to human bodies. Further, a polymerizablemonomer having an acid group in its molecule is preferable as acomponent capable of particularly imparting high adhesion to dentin tothe adhesive. Therefore, a combination of (meth)acrylate and apolymerizable monomer having an acid group, such as carboxyl group, itsanhydride group, phosphoric acid group or sulfonic acid group, is alsopreferably employed.

Examples of the monofunctional (meth)acrylates employable in theinvention include alkyl (meth)acrylates, such as methyl (meth)acrylate,ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, hexyl(meth)acrylate, 2-ethylhexyl (meth)acrylate, dodecyl (meth)acrylate,lauryl (meth)acrylate, cyclohexyl (meth)acrylate, benzyl (meth)acrylateand isobornyl (meth)acrylate; hydroxyalkyl esters of (meth)acrylicacids, such as 2-hydroxyethyl (meth)acrylate, 2- or 3-hydroxypropyl(meth)acrylate, 4-hydroxybutyl (meth)acrylate, 5-hydroxypentyl(meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 1,2- or1,3-dihydroxypropyl mono(meth)acrylate and erythritolmono(meth)acrylate; polyethylene glycol mono(meth)acrylates, such asdiethylene glycol mono(meth)acrylate, triethylene glycolmono(meth)acrylate, polyethylene glycol mono(meth)acrylate andpolypropylene glycol mono(meth)acrylate; (poly)glycol monoalkyl ether(meth)acrylates, such as ethylene glycol monomethyl ether(meth)acrylate, ethylene glycol monoethyl ether (meth)acrylate,diethylene glycol monomethyl ether (meth)acrylate, triethylene glycolmonomethyl ether (meth)acrylate, polyethylene glycol monomethyl ether(meth)acrylate and polypropylene glycol monoalkyl ether (meth)acrylate;fluoroalkyl esters of (meth)acrylic acids, such as perfluorooctyl(meth)acrylate and hexafluorobutyl (meth)acrylate; silane compoundshaving (meth)acryloxyalkyl groups, such asγ-(meth)acryloxypropyltrimethoxysilane andγ-(meth)acryloxypropyltri(trimethylsiloxy)silane; and (meth)acrylateshaving heterocyclic rings, such as tetrafurfuryl (meth)acrylate.

Examples of the polyfunctional (meth)acrylates include:

poly(meth)acrylates of alkanepolyols, such as ethylene glycoldi(meth)acrylate, propylene glycol di(meth)acrylate, butylene glycoldi(meth)acrylate, neopentyl glycol di(meth)acrylate, hexylene glycoldi(meth)acrylate, trimethylolpropane tri(meth)acrylate andpentaerythritol tetra(meth)acryalte;

polyoxyalkanepolyol poly(meth)acrylates, such as diethylene glycoldi(meth)acrylate, triethylene glycol di(meth)acrylate, polyethyleneglycol di(meth)acrylate, dipropylene glycol di(meth)acrylate,polypropylene glycol di(meth)acrylate, dibutylene glycoldi(meth)acrylate and dipentaerythritol hexa(meth)acrylate;

aliphatic or aromatic di(meth)acrylates represented by the followingformula (1):

wherein R is a hydrogen atom or a methyl group, m and n are the same ordifferent and are each a number of 0 to 10, and R¹ is any one of

aliphatic or aromatic epoxy di(meth)acrylates represented by thefollowing formula (2):

wherein R is a hydrogen atom or a methyl group, n is a number of 0 to10, and R¹ is any one of

; and

polyfunctional (meth)acrylates having a urethane bond in a molecule,which are represented by the following formula (3):

wherein R is a hydrogen atom or a methyl group, and R¹ is any one of

Of the above monofunctional (meth)acrylates, particularly preferablyused are alkyl (meth)acrylates, such as methyl (meth)acrylate and ethyl(meth)acrylate; (meth)acrylates having hydroxyl group, such as2-hydroxyethyl (meth)acrylate, 1,3-dihydroxypropyl mono(meth)acrylateand erythritol mono(meth)acrylate; and (meth)acrylates having ethyleneglycol chain in a molecule, such as triethylene glycol mono methyl ether(meth)acrylate and triethylene glycol mono(meth)acrylate.

Of the above polyfunctional (meth)acrylates, particularly preferablyused are di(meth)acrylates having ethylene glycol chain in a molecule,such as triethylene glycol di(meth)acryalte and polyethylene glycoldi(meth)acrylate;

compounds represented by the following formula (1)-a:

wherein R, m and n have the same meanings as in the formula (1);

compounds represented by the following formula (2)-a:

wherein R has the same meaning as in the formula (2); and

compounds represented by the following formula (3)-a:

wherein R has the same meaning as in the formula (3).

The above monomers can be used singly or in combination of two or morekinds.

Examples of the polymerizable monomers having an acid group in amolecule include (meth)acrylic acid ester monomers having carboxylicacid group or carboxylic acid anhydride group, such as (meth)acrylicacid or its anhydride, 1,4-di(meth)acryloxyethylpyromellitic acid,6-(meth)acryloxyethylnaphthalene-1,2,6-tricarboxlyic acid,N-(meth)acryloyl-p-aminobenzoic acid, N-(meth)acryloyl-o-aminobenzoicacid, N-(meth)acryloyl-m-aminobenzoic acid,N-(meth)acryloyl-5-aminosalicylic acid,N-(meth)acryloyl-4-aminosalicylic acid, 4-(meth)acryloxyethyltrimelliticacid or its anhydride, 4-(meth)acryloxybutyltrimellitic acid or itsanhydride, 4-(meth)acryloxyhexyltrimellitic acid or its anhydride,4-(meth)acryloxydecyltrimellitic acid or its anhydride,2-(meth)acryloyloxybenzoic acid, 3-(meth)acryloyloxybenzoic acid,4-(meth)acryloyloxybenzoic acid, β-(meth)acryloyloxyethylhydrogensuccinate, β-(meth)acryloyloxyethyl hydrogenmaleate,β-(meth)acryloyloxyethyl hydrogenphthalate,11-(meth)acryloyloxy-1,1-undecanedicarboxylic acid and p-vinylbenzoicacid; (meth)acrylic acid ester monomers having phosphoric acid group,such as (2-(meth)acryloxyethyl)phosphoric acid,(2-(meth)acryloxyethylphenyl)phosphoric acid and10-(meth)acryloxydecylphosphoric acid; and monomers having sulfonic acidgroup, such as p-styrenesulfonic acid and2-acrylamido-2-methylpropanesulfonic acid.

The above monomers having an acid group can be used singly or incombination. It is preferable to use the polymerizable monomer having anacid group in an amount of 2 to 20 parts by weight based on 100 parts byweight of the total of the polymerizable monomers (a).

Examples of the (meth)acrylate polymers (b) contained in the adhesive ofthe invention include non-crosslinking polymers, such as polymethyl(meth)acrylate, polyethyl (meth)acryalte, a methyl (meth)acryalte/ethyl(meth)acrylate copolymer, a methyl (meth)acrylate/butyl (meth)acrylatecopolymer and a methyl (meth)acrylate/styrene copolymer; andcrosslinking polymers, such as a methyl (meth)acrylate/ethylene glycoldi(meth)acrylate copolymer, a methyl (meth)acrylate/triethylene glycoldi(meth)acrylate copolymer and a copolymer of methyl (meth)acrylate anda butadiene type monomer.

It is also possible to use inorganic particles wherein metal oxides ormetal salts are coated with the above alkyl methacrylate polymers. Thecomponent (b) or the component (c) may be used after mixed with thecomponent (a).

In the adhesive of the invention, the component (b) is used in an amountof 0 to 70 parts by weight and the component (c) is used in an amount of3 to 25 parts by weight, based on 20 to 90 parts by weight of thecomponent (a), with the proviso that the total of the components (a),(b) and (c) is 100 parts by weight.

To the adhesive of the invention, camphorquinone, organic solvents, suchas acetone, coloring agents, and polymerization inhibitors, such ashydroquinones, can be added in appropriate amounts.

The adhesive of the invention is applied to dental or surgical use. Whenthe adhesive of the invention is applied to dental or surgical use, itis preferable to use it after pretreatment of teeth. Examples of thepretreatments include an etching treatment of an adhesive surface withan acid solution, a modification treatment of an adhesive surface with aprimer, and an etching and modification treatment of an adhesive surfacewith a primer having etching ability. Examples of the acid solutionsused for the etching treatment include a phosphoric acid aqueoussolution having a concentration of 5 to 60% by weight and an aqueoussolution containing 10% by weight of citric acid and 3% by weight offerric chloride. The primer used for the modification treatment of anadhesive surface is, for example, an aqueous solution of a concentrationof 20 to 50% by weight containing 2-hydroxyethyl (methyl) acrylate and1,3-dihydroxypropyl mono(meth)acrylate. As the primer having etchingability used for the etching and modification treatment of an adhesivesurface, an aqueous solution containing an organic acid (including amonomer having an acid group) and a component to modify decalcificateddentin and thereby accelerate diffusion of the adhesive into the dentinis preferably employed. Examples of the components to acceleratediffusion of the adhesive into dentin include monomers having hydroxylgroup, such as alkylene glycol, polyalkylene glycol, 2-hydroxyethyl(meth)acrylate and 1,3-dihydroxypropyl mono(meth)acrylate, andpolyethylene glycol (meth)acrylate.

The polymerization initiator paste composition of the invention and theadhesive using the paste composition have good biocompatibility and arepreferably used for adhesive restoration of tissues, e.g., adhesiverestoration of teeth, protection of wounded hard or soft tissues oradhesive fixation in surgical treatment.

INDUSTRIAL APPLICABILITY

The polymerization initiator paste composition of the invention iscontrolled to have a given consistency by adding specific particles toan organoboron compound that is liquid at room temperature, andtherefore, it becomes possible to fill the paste composition in acontainer such as a tube or a syringe and to extrude a necessary amountof the paste composition from the container when the paste compositionis used. Further, the amount of the paste composition used can bemeasured, not in weight, but in length of the extruded pastecomposition. Moreover, because the polymerization initiator pastecomposition of the invention has the above-mentioned consistency, it canbe easily extruded from a container such as a syringe, and the shape ofthe extruded polymerization initiator paste composition is not brokenand can be retained as it is. Accordingly, from the length of theextruded polymerization initiator paste composition, the amount of thepolymerization initiator can be accurately measured.

The dental or surgical adhesive of the invention comprises thepolymerization initiator paste composition and a polymerizable monomerthat is packaged separately from the paste composition, and the amountof the polymerization initiator can be accurately measured in length.Further, by making both the components pasty, mixing of those componentsbecomes very easy.

In the dental or surgical adhesive kit of the invention, thepolymerization initiator composition is a paste, and therefore, thecomposition can be quantitatively determined and used by measuring thecomposition in length. Moreover, mixing of the composition with apolymerizable monomer is very easy.

EXAMPLE

The present invention is further described with reference to thefollowing examples, but it should be construed that the invention is inno way limited to those examples.

Measuring Methods

Preparation of Polymerization Initiator Paste Composition ContainingOrganoboron Compound

(1) In a nitrogen atmosphere, given amounts of a filler and anorganoboron compound (including partially oxidized organoboron compound)were mixed by a spatula to prepare a polymerization initiator pastecomposition. The paste compositions of Examples 10 and 11 furthercontained acetone in an amount of 15% by weight and 13% by weight,respectively.

(2) The polymerization initiator paste composition obtained in the abovestep (1) was filled in a syringe having a diameter of 10 mm in anitrogen atmosphere, and the syringe was placed in an aluminum coatingmultilayer bag with a zipper and stored in a nitrogen box.

(3) In the preparation of an adhesive, a given length of each componentwas extruded by the use of a syringe with a discharge opening having aninner diameter of 0.9 mm or 1.8 mm, and the components were mixed.

Measurement of Consistency

The consistency was measured in accordance with a method described inISO4823. That is to say, at 25° C., 0.5 ml of the composition wasextruded from a syringe (opening: 10 mm) having a diameter of 10 mm andplaced on a surface of a first glass plate. On the composition, a secondglass plate and a weight (total: 300g±3g) were gently placed, and after1 minute, the weight was removed. Then, many pairs of parallel lines incontact with an outer edge of the shape of the composition having spreadon the glass plate were drawn, and the maximum value and the minimumvalue between the parallel lines were measured. An average of themeasured values was calculated and expressed in the unit of 1 mm.

Examples 1-11

Tributylboron (oxygen addition quantity: 0.8% by mol) and a filler shownin Table 1 were mixed in the same manner as described above to prepare apolymerization initiator paste composition.

The polymerization initiator paste composition was filled in acommercially available 2.5 ml plastic syringe and discharged from adischarge nozzle (inner diameter: 0.9 mm or 1.8 mm, length: 10 mm),followed by examination of discharge properties of the polymerizationinitiator paste composition.

In Table 1, AA means that the composition was well discharged; BB meansthat the composition was badly discharged; and CC means that thecomposition was not discharged.

Then, adhesion strength of the polymerization initiator pastecomposition to dentin was measured in the following manner.

(1) Under water pouring, a lip side surface of a front tooth of cattlewas cut to expose dentin, and the dentin was polished with emery paperof No. 600 to form an adhesive surface.

The adhesive surface was dried, then treated with an etching solutioncontaining 10% by weight of citric acid and 3% by weight of ironchloride for 10 seconds, washed with water for 10 seconds and thensubjected to air blow drying for 15 seconds. Thereafter, a cellophanetape having a circular hole of 4 mm diameter was attached to theadhesive surface to specify the adhesion area.

(2) On a Dappen dish, 4 drops (0.32 g) of a polymerizable monomerconsisting of MMA/4-META=95/5 (parts by weight) and the polymerizationinitiator paste composition in such an amount that the amount of TBBObecame about 0.07 g were placed, and they were lightly mixed for 10seconds to give a resin mud.

(3) The resin mud was applied onto the adhesive surface prepared in theabove step (1), and an acrylic bar was bonded to prepare an adhesiontest sample. The adhesion test sample was allowed to stand for 30minutes at room temperature, immersed in distilled water at 37° C. for24 hours and then subjected to a tensile test to measure adhesionstrength between the acrylic bar and the dentin. The adhesion strengthis an average of measured values of three test samples. TABLE 1 Pastedischarge properties Dentin adhesion Inner Inner TBB content strengthConsistency diameter diameter Filler (wt %) (MPa)*¹² (mm) 0.9 mm 1.8 mmEx. 1 PMMA pearl (0.34 μm)*¹ 72 17.0 41 AA AA Ex. 2 crosslinked PMMApearl (1 μm)*² 56 13.7 33 AA AA Ex. 3 PMMA pearl (0.34 μm)*³ 34 18.2 16CC BB Ex. 4 PMMA pearl (30 μm)*⁴/(0.34 μm)*³ = 1/1 50 17.4 30 AA AA Ex.5 SiO₂ (16 nm)*⁵ 86 11.9 60 AA AA Ex. 6 SiO₂ (16 nm)*⁶ 83 13.1 29 AA AAEx. 7 SiO₂ (7 nm)*⁷ 17 14.4 32 AA AA Ex. 8 ZrO₂ (50 nm)*⁸ 53 19.9 28 AAAA Ex. 9 PMMA pearl (0.34 μm)/SiO₂*⁹ = 9/1 63 15.3 28 AA AA Ex. 10 SiO₂(16 nm)*¹⁰ 69 13.8 33 AA AA Ex. 11 crosslinked PMMA pearl (1 μm)*¹¹ 4615.2 26 BB AANotes:*¹Soken Kagaku MP2200,*²Soken Kagaku MR-2G,*³Sekisui Kaseihin Kogyo MB8,*⁴Shinnakamura D-250 ML,*⁵Nippon Aerosil R972,*⁶Nippon Aerosil R972,*⁷Denki Kagaku Kogyo FB-6D,*⁸Adachi Shinsangyo Nanotec ZrO₂,*⁹Nippon Aerosil R972,*¹⁰Nippon Aerosil R972,*¹¹Nippon Aerosil R972,*¹²immersion in water at 37° C. for 24 hours

1. A polymerization initiator paste composition comprising: (A) an organoboron compound, and (B) particles having an average particle diameter of 0.001 to 50 μm and inert to the organoboron compound (A), in an amount of 4 to 400 parts by weight based on 100 parts by weight of the organoboron compound (A), said paste composition having a consistency, as measured at 25° C. under a load of 300 g in accordance with a method defined in ISO4823, of 15 to 100 mm.
 2. The polymerization initiator paste composition as claimed in claim 1, wherein the organoboron compound (A) is liquid at 25° C.
 3. The polymerization initiator paste composition as claimed in claim 1, wherein the organoboron compound (A) is trialkylboron or a partial oxide thereof.
 4. The polymerization initiator paste composition as claimed in claim 1, wherein the particles (B) are polymer particles which are inert to the organoboron compound (A) and are insoluble but homogeneously dispersible in the organoboron compound (A).
 5. The polymerization initiator paste composition as claimed in claim 1, wherein the particles (B) are metal oxide particles having an average particle diameter of 0.001 to 10 μm and inert to the organoboron compound (A).
 6. The polymerization initiator paste composition as claimed in claim 1, wherein the particles (B) are mixtures of fine particles (b1) having an average particle diameter of not less than 0.001 μm and less then 1 μm and particles (b2) having an average particle diameter of 1 μm to 50 μm.
 7. The polymerization initiator paste composition as claimed in claim 1, which is contained in a sealed container having impermeability to air and water vapor and having a nozzle that is capable of extruding the polymerization initiator paste composition and has a nozzle tip inner diameter of 0.4 to 4 mm and a nozzle length of 2 to 50 mm.
 8. The polymerization initiator paste composition as claimed in claim 7, wherein the container having impermeability to air and water vapor is a tube or a syringe.
 9. A dental or surgical adhesive comprising: a polymerization initiator paste composition which comprises: (A) an organoboron compound, and (B) particles having an average particle diameter of 0.001 to 50 μm and inert to the organoboron compound (A), in an amount of 4 to 400 parts by weight based on 100 parts by weight of the organoboron compound (A), and has a consistency, as measured at 25° C. under a load of 300 g in accordance with a method defined in ISO4823, of 15 to 100 mm, and (C) a polymerizable monomer which is packaged separately from the polymerization initiator paste composition.
 10. The dental or surgical adhesive as claimed in claim 9, wherein the organoboron compound (A) is trialkylboron or a partial oxide thereof.
 11. A dental or surgical adhesive kit comprising: a first container filled with a polymerization initiator paste composition which comprises: (A) an organoboron compound, and (B) particles having an average particle diameter of 0.001 to 50 μm and inert to the organoboron compound (A), in an amount of 4 to 400 parts by weight based on 100 parts by weight of the organoboron compound (A), has a consistency, as measured at 25° C. under a load of 300 g in accordance with a method defined in ISO4823, of 15 to 100 mm, and is extrudable from the container, and a second container filled with a polymerizable monomer (C) which is contained separately from the polymerization initiator paste composition.
 12. The dental or surgical adhesive kit as claimed in claim 11, wherein the first container can contain the polymerization initiator paste composition without substantially bringing the paste composition into contact with air and water vapor and has a nozzle capable of extruding the polymerization initiator paste composition and having a nozzle tip inner diameter of 0.4 to 4 mm and a nozzle length of 2 to 50 mm.
 13. The dental or surgical adhesive kit as claimed in claim 12, wherein the nozzle tip inner diameter of the first container is in the range of 0.5 to 3 mm.
 14. The dental or surgical adhesive kit as claimed in claim 11, wherein the organoboron compound (A) is trialkylboron or a partial oxide thereof.
 15. The dental or surgical adhesive kit as claimed in claim 11, wherein the polymerizable monomer has a consistency equal to that of the polymerization initiator paste composition. 